Method and apparatus for resonant rotational oscillator

ABSTRACT

A method and apparatus for resonant rotational oscillator have been disclosed. In one version a moving coil is mounted on a rotating member. By using a magnetic assembly and the moving coil the rotating member is made to rotate.

FIELD OF THE INVENTION

The present invention pertains to rotational oscillators. Moreparticularly, the present invention relates to a method and apparatusfor resonant rotational oscillator.

BACKGROUND OF THE INVENTION

Resonant rotational oscillators are used, generally, to deflect, forexample, a laser beam during scanning. For example, a resonantrotational oscillator might be used in a checkout stand at a store aspart of the scanner for identifying product purchased, for example, byscanning for a bar code. A slow scanner or one with a limited deflectionangle may slow the scanning process or make it more difficult to scan.This presents a problem.

A slow scanner, slower operation, and difficulty in scanning are likelyto lead to more expensive operation. This presents a technical problemfor which a technical solution is needed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example and not limitation in thefigures of the accompanying drawings.

FIG. 1 illustrates one embodiment of the invention showing an End, Side,and Top view.

FIG. 2 illustrates various embodiment of the invention showingalternative flexure bends.

FIG. 3 illustrates one embodiment of the invention showing an arm withembedded mirror.

FIG. 4 illustrates various embodiments of the invention.

FIG. 5 illustrates various embodiments of the invention.

FIG. 6 illustrates an embodiment of the present invention.

FIG. 7 illustrates an embodiment of the invention showing a crosssectional view.

FIG. 8 illustrates various embodiments of the invention.

DETAILED DESCRIPTION

A method and apparatus for resonant rotational oscillator is disclosed.

In one embodiment of the invention, a rotational mechanical oscillatorsimultaneously achieves high resonant frequency and large angularoscillation amplitude (also denoted angular displacement or angularrotation).

In one embodiment of the invention, the device may be used with anattached mirror to optically direct or scan a light beam or opticalimage. Sometimes these embodiments are referred to as optical scannersor resonant scanners.

In one embodiment of the invention, the optical resonant scanner has amirror attached to a spring that is constrained to rotate about an axis,and a motor means to drive the oscillation. The inherent rotationalspring-mass system creates a mechanical resonant situation allowing theattached mirror to rotate. A light beam reflecting off the mirrorexecutes a rotational resonant scanning motion. Various sizes and shapesof mirrors may be used as needed for a particular optical application(e.g. round, oval, rectangular, square, octagonal, hexagonal, arbitraryshape). The associated mass of the assembly is generally the primarydeterminant of the resonant frequency. Various architectures of motorsmay also be used. The motor is used to create sufficient torque to drivethe resonance to the desired amplitude. The mass of the motor may becomean issue as a large motor may contain excessive mass to further limitthe resonant frequency. The spring in the system generally takes one oftwo forms. The first is a torsion bar and the second is a system ofcrossed flat springs.

In one embodiment of the invention, a torsion bar scanner design uses athin rod which acts as a rotational spring when forced to twist aboutits longitudinal axis. In one embodiment of the invention one end of atorsion bar is fixed while a mirror is attached at the other end. In oneembodiment the torsion rod is clamped at both ends and the mirrorcentrally located on the free length of the torsion rod. In oneembodiment of the invention, tensile loading of the torsion rod is usedto increase the cross-axis vibrational resonant frequency.

In one embodiment of the invention, a crossed flat spring (or crossedflexure) scanner architecture is used. In one embodiment of theinvention, the crossed flexure scanner architecture uses a system offlat spring elements with a pair of adjacent flat springs mounted toform an “X”. Frequently two such pairs are used, with the two pairsseparated to increase cross-axis stiffness, and the primary mass(generally the mirror) suspended between the pairs. The rotational axisis at the line formed by the apparent crossing of the two springs (i.e.middle of the “X”). This embodiment of the present invention has verygood cross-axis stiffness.

In one embodiment of the invention, the crossed flexures constructionused consists of pairs of crossed flat spring elements clamped at oneend to a rigid base and clamped at the other end to a mechanism to holda mirror, forming an assembly that is free to rotate. In one embodimentof the invention, the moving mass is located at or near the rotationalaxis.

In one embodiment of the invention, to achieve indefinite spring life(with respect to the application) at large deflection angles, the ratioof spring length and spring thickness is determined by the endurancelimit stress allowed in the spring material. A longer length, or thinnerthickness, of a given spring material will have a lower stress for agiven deflection. Countering the lowered stress of a longer spring isthe higher moment of inertia of the oscillating member. This moment ofinertia is very important since an increase in moment of inertia reducesthe resonant frequency, for a given spring stiffness, and thus reducesthe performance of the scanner.

In one embodiment of the invention, an optimized design of the crossedflexure scanner architecture minimizing the total moment of inertia ofthe rotating system is used thereby maximizing performance. Anappropriate metric of performance is the product of frequency andmaximum deflection angle. This metric of performance is referred to asperformance metric denoted PM and is calculated by this equation:PM=frequency*angle  Equation 1

-   -   where:    -   frequency=hertz of operation of the resonant rotational        oscillator; and    -   angle=degrees of angle deflection (maximum) of the moving member        when operating at the frequency.

In one embodiment of the invention, the design and fabrication of a highperformance crossed flexure resonant scanner uses an optimized design ofthe crossed flexure scanner architecture minimizing the total moment ofinertia of the rotating system, thereby maximizing the performancemetric of the product of frequency and maximum deflection angle (seeEquation 1). The resultant device is capable of much higher frequenciesat a given maximum angle or much larger angles at a given frequency thanprevious designs. The design is more manufacturable and reliable becauseof careful attention to the optimization process as is described.

In one embodiment of the invention a PM of greater than 12500 HzDegreesis achieved.

In one embodiment of the invention, described herein are designtechniques for an optimized crossed flexure scanner architectureminimizing the total moment of inertia of the rotating system.

In one embodiment of the invention, to optimize the scanner systemperformance metric stress in the flexures, due to bending, limits themaximum deflection angle and is taken into account. That stress, for agiven bend angle, is proportional to the square of the flexure thicknessand inversely proportional to the square of the flexure length. Thestiffness of a flexure is linearly proportional to the flexure (beam)width (W), proportional to the cube of the flexure thickness, andinversely proportional to the cube of the flexure length. The resonantfrequency of a spring-mass system (using the linear system terminologyrather that the rotational system terminology) is proportional to thesquare root of the ratio of the spring stiffness (k) to the moving mass(m), f=√(k/m). The mass moment of inertia (I) (or just moment ofinertia) is the sum of the product of masses (m) of all mass elementsand their respective radius (r) from the rotational axis squared,I=Σmr². So, to maximize the Performance Metric (PM), which is theproduct of frequency and maximum angle, we minimize mass and maximizethe ratio of flexure length (L) and flexure thickness (t), thus PM isproportional to √(WL/tl).

In one embodiment of the invention, the total mass is generally the sumof the mirror, or similar moving mass, which is fixed for a givenoptical application, and the other “unintended masses”. The mirrorsupport is considered an unintended mass, as are the moving parts of amotor and any supports required to couple the flexures and the mirrormount. The flexure to mirror mount couplings are generally at the farend of the length of the flexures so their contribution to diminishingPM is proportional to mL^(1.5). Due to this effect, L is kept to amodest length so that the moment of inertia of the combined flexure tomirror mount couplings is small compared to the mirror. The other effectto minimize is due to the mirror mount. The mass of the mirror mountincreases linearly with the width of the mirror plus the width of theflexures plus the width of a motor, any sensors, etc. Additionally withincreased flexure width the stiffness of the flexure increases linearly,so, the flexure widths are also to be kept relatively small relative tothe diameter of the mirror. Additionally, the total arm length (end toend of moving element) should be kept to a minimum to minimize resonanceproblems from the arm itself.

In one embodiment of the invention, therefore, the optimum design rulesfor a high Performance Metric resonant scanner, with an architecture asshown in FIG. 1, are as follows, normalized assuming all materialsexcept the steel flexures have a similar mass density. Importantly, keepall masses small compared to the mirror and locate them as close to therotational axis as possible. To keep the arm moment of inertia small,make the primary width of the arm≦mirror diameter/4, and make the widthof each flexure approximately equal to ½ of the length of each flexure.Each flexure should have a flexing length, excluding the clamped ends,approximately equal to ½ of the mirror diameter. The crossed flexuresshould cross each other at their centers and at an angle of 90°.Finally, a flexure thickness is chosen that, in conjunction with thetotal moment of inertia, which will primarily be from the mirror, andproduces the desired resonant frequency. This minimizes the moment ofinertia.

These are generalized rules that can guide the designer to optimize ascanner design for other special cases and applications.

In one embodiment of the invention, shown generally FIG. 1, shows threeorthogonal views of an embodiment of the present invention labeled End,Top and Side. All views clearly show a Base 10 which is important as arigid and massive foundation for the reaction forces and torques createdby resonant oscillation. The Top view shows the Rotational Axis 11formed by the four Crossed Flexures 12. The crossing can be clearly seenin the End view where the flexures appear to cross at 12′. OscillatingMirror 13 is shown as dashed lines in each view to clarify anddifferentiate from the scanner mechanics. The Mirror 13 is attached toMounting Arm 14 which supports and couples the mirror to the crossedflexure system. The mirror, or other application load, in a resonantscanner is the element that must rotate. That is the whole point of thescanner.

In one embodiment of the invention, ideally, the mirror is the largestsingle moving mass element in the system. The mass and moment of inertiaof all other parts are to be minimized compared to the mirror in orderto maximize performance. The mass moment of inertia (I) (or just momentof inertia) is the sum of the product of masses (m) of all mass elementsand their respective radius (r) from the rotational axis squared,I=Σmr². Notice in the end view of FIG. 1 that the center of the mirroris very close to the rotational axis 11. By design, the rotational axisis placed at the location where the moment of inertia is the minimum. Ifall other masses are minimized then that position is also very close tothe center of the mirror. Notice also, in the end view of FIG. 1 thatthe flexures cross at 90°. That puts the Flexure Spacers 15, whichcouple and separates the Flexures 12 and the Mounting Arm 14, at thesmallest possible radius from the rotational axis for a given flexurelength, thereby minimizing their moment of inertia contribution. The 90°crossing also maximizes cross-axis stiffness. Although, a differentangle could be an appropriate trade-off with moment of inertia for aspecific application.

In one embodiment of the invention, this optimization also minimizes theeffect of a change in temperature causing expansion of the flexuresthereby causing a shift in the resonant frequency. Any temperaturechange from the design point will cause the flexures to change strength,stiffness and physical dimensions, particularly length, according to thebulk properties of the flexure material. All such changes will changethe resonant frequency of the scanner. However, if as described above,the center of mass is at the rotational axis, which is at the centercrossing point of the flexures, then the mass center won't move with atemperature change, which would have caused a large decrease in resonantfrequency.

In one embodiment of the invention, the construction technique for thepresent invention, the Mounting Arm 14 is a major component. Ideally, itshould be both stiff and low mass. A high specific stiffness material isa good choice but geometry is also extremely important. A less stiffmaterial made thicker is stiffer than a stiffer material made thinner,by the cube of the thickness. Epoxy-fiber glass printed circuit board(PCB) material, like FR4, is an excellent choice, especially consideringits low material and fabrication costs. Additionally, conductive tracescan be printed (or etched) on it to aid such tasks as routing conductorsfor a motor or position sensor. This provides high manufacturability andreliability while being very cost effective.

In one embodiment of the invention, a construction technique for thepresent invention, the Flexure Spacers 15, provide an opportunity tochange performance. Again, the Flexure Spacers 15 want to be both stiffand low mass, with the same arguments as for the Mounting Arm 14. Inthis case an excellent choice for a Flexure Spacer is a nylon spacerswaged between a Flexure 12 and the Mounting Arm 14 with a hollow metaleyelet. This provides high rigidity and strength, low mass and low cost.

In one embodiment of the invention, the design for the presentinvention, a relatively efficient and low moment of inertia moving coilmotor was chosen. The motor is composed of a Moving Coil 17 attached tothe Mounting Arm 14, a fixed permanent Magnet 18, and a fixed Back-ironAssembly 16. The Moving Coil 17 is a preformed coil, of fine magnetwire, glued to the Arm with Epoxy, and centered on the rotational axisfor highest efficiency and lowest moment of inertia. In this embodimentthe coil is moving, so the coil leads need to be routed from therotating assembly to the fixed part of the device and ultimately tomotor drive electronics.

In one embodiment of the invention, a moving magnet design could have alower moment of inertia, however, an efficient moving magnet designrequires a fixed back-iron surrounding the moving magnet. The strongattraction of the magnet to the back-iron may present an issue with aflexure suspended system.

In one embodiment of a construction technique for the present invention,the chosen Flexure 12 material was hardened stainless steel. Higherstrength, more exotic materials are available but with only marginallybetter strength but with significantly higher material and fabricationcosts. The more affordable material choice was made taking advantage ofthe greatly improved Performance Metric of the current invention.

In one embodiment of the design for the present invention, since thechosen Flexure 12 material is stainless steel, which is electricallyconductive, two of the Flexures could be used to couple the moving coilleads from the rotating assembly to the fixed part of the device. Theconduction path for each of the two moving coil leads is then,separately, from a moving coil end, soldered to an electrical trace onthe Arm, to and through a Spacer eyelet, to and through a Flexure, andto the Base where the Flexure is mounted with an electrically InsulatedCoupling 20 to the Base with a Screw 21. At the Screw, a wire can beconveniently attached to route the conductor to the motor driveelectronics.

In one embodiment of both a design and a construction technique for thepresent invention, the Base 10 can be fabricated from an insulatingmaterial like FR4. This technique would be practical particularly forsmall Resonant Scanners where the Base could be formed from FR4 andstill practically keep a high thickness to length ratio required to makethe base appropriately rigid. This technique would simplify theelectrical coupling from the Flexure to the Base since the Basesubstrate material would be nonconductive thereby eliminating the needfor an Insulated Coupling. Further, such a base made of FR4 could be aPCB with conductive traces printed on the Base at the points of flexurecouplings to act as the coil conductors to the motor drive electronics,thereby possibly eliminating wires. Further still, conceivably, thecircuit for the motor drive electronics, or other control or processingelectronics, could be printed and installed on the PCB Base.

In one embodiment of the design for the present invention, a mirrorPosition Sensor 19 can be added. Appropriately, it would look at thebottom center of the attached mirror and accurately report its angularposition. Precise and accurate mirror position information is necessaryfor some high technology applications and improves the ability of themotor drive electronics to control the resonant frequency and/oramplitude of deflection (i.e. angle of deflection).

In one embodiment of the design for the present invention, the motor orother driving means could, for example, take the form of a movingmagnet, a moving coil, or a bulk effect device like piezoelectric ormagnetostrictive.

In one embodiment of the design for the present invention, the motorcould be located predominately under the moving mirror, or intertwinedin the crossed flexures, to minimize the total length of the device.

In one embodiment of the design for the present invention, the motorcould be located outside of the flexures such that the mirror is notadjacent to the motor.

In one embodiment of the design for the present invention, the flexurematerial could be non-metallic, for example, plastic, graphite, ceramic,glass, or a composite.

The embodiment of FIG. 1 shows the ends of the flexures bent at 45° tofacilitate mounting. Other bend angles, on either end of each flexure,could be used as appropriate for alternative mounting schemes. Forexample, the arm end of the flexure could be bent into a verticalorientation, rather than horizontal as in FIG. 1, to better mount to analternative arm design.

FIG. 2 shows generally at 200 various alternative flexure bends asviewed from an end view, for example, the End view of FIG. 1. Only asingle flexure is shown. In practice a mirror image (about the verticalaxis) flexure would also be used, so that the two flexures would cross(for example, as shown in FIG. 1 at 12′) at approximately 90°.

In one embodiment of the design for the present invention, the flexurescould contain openings, for example, slots or holes, to modify theirstiffness beyond what is determined by their simple outline dimensions.

In one embodiment of the design for the present invention, the flexurescould be rigidly attached to the base and arm by means other thanscrews, for example, riveting, welding, soldering, gluing, etc.

In one embodiment of the design for the present invention, the flexures,or flexure pairs, could be formed monolithically thereby minimizingattachments and flexure misalignments.

In one embodiment of the design for the present invention, the flexures,or flexure pairs, could be formed in the split-band configuration in anattempt to further increase flexure symmetry.

In one embodiment of the design for the present invention, the arm couldbe a single molded piece incorporating all required functions betweenthe mirror and the flexures (for example, the spacers). For example, itcould be bent up to attach to the flexure then flattened to mount themotor then dip to support the mirror at the exact center of rotation.

FIG. 3, illustrates, generally at 300, an arm 14 with an embedded mirror13 and integral flexure supports 15′ which perform the same function asspacers (e.g. 15). At 12 are where the flexures are attached. As may beseen the arm 14 has an indentation where mirror 13 is mounted. In thisway the arm 14 supports the mirror 13 at the exact center of rotation.

FIG. 4, illustrates, generally at 400, various embodiments of thepresent invention. At 402 are shown flexures where at the crossing 404they are fixedly attached to each other. Since the rotational axis is atthe point indicated by 404, the flexures may be fixedly attached at thispoint. Alternatively, 402 may be constructed of an integral part. At 406is a top view of such a single flexure unit showing the crossing 404 andthe top mounting points on the flexure 401 and 403.

FIG. 5, illustrates, generally at 500, various embodiments of thepresent invention. At 502 is shown a top view of a flexure having a slot503. At 506 is shown a top view of a flexure having holes 507. Note thatthe holes may be placed at various locations (not shown in FIG. 5 at506) At 510 is an embodiment showing a top view where the flexures 512and 516 are “multi-fingered” (two “fingers” at 513 and 515 for flexure512; two “fingers” at 517 and 519 for flexure 516) and the “fingers” areintertwined.

FIG. 6, illustrates an embodiment of the present invention.

FIG. 7, illustrates, generally at 700, one embodiment of the inventionshowing a cross sectional view of an expanded not to scale view of amoving coil 17 mounted on the moving arm 14, and a back iron assembly 16and a magnet 18. At 702 is a support (non-magnetic) for attaching themagnet 18 to the back iron assembly 16. At 704 are coils of wire of themoving coil 17 for explanation purposes. At 14 is the moving arm onwhich the moving coil 17 is mounted. Note that the drawing is not toscale. When there is no current flowing through the coils of wire 704 ofthe moving coil 17 the moving coil 17 which is attached to the movingarm 14 is at rest as shown in FIG. 7. When current flows in a firstdirection through the coils of wire 704 of the moving coil 17 the movingcoil 17 this will produce a magnetic field which will interact with themagnet 18 and create a torque that will cause the moving coil 17 torotate and since it is attached to the moving arm 14 will cause themoving arm to rotate, for example clockwise as viewed from the page ofFIG. 7. When current is removed the restorative forces of the flexureswill tend to return the moving arm 14 (and the attached moving coil 17)to its at rest position as shown in FIG. 7. Likewise when a currentflows in a direction opposite to the first direction current flow, themoving coil 17 and moving arm 14 will rotated in a counter-clockwisedirection. What is to be appreciated by one of skill in the art is thatusing for example, the right hand rule it can be easily seen that torqueabout the rotational axis of the moving arm 14 may be produced by themoving coil 17.

In one embodiment of the invention, for example as illustrated in FIG. 7the torque created by the moving coil motor (or not shown a movingmagnet motor) is symmetrical about the rotational axis of the rotatingassembly (which has components such as, but not limited, to the movingcoil, the mirror, the moving arm, etc.). For example, in FIG. 7 at point710 is denoted the rotational axis of the rotating assembly.

In one embodiment of the invention, for example as illustrated in FIG. 7the center of the mass of the rotating assembly (which has componentssuch as, but not limited, to the moving coil, the mirror, etc. mountedon it) is at the center of rotation of the rotating assembly, forexample, as illustrated in FIG. 7 at point 710 a dot.

In one embodiment of the invention, for example as illustrated in FIG. 7the torque created by the moving coil motor (or not shown a movingmagnet motor) is symmetrical about the rotational axis of the rotatingassembly (which has components such as, but not limited, to the movingcoil, the mirror, the moving arm, etc.). For example, in FIG. 7 at point710 is denoted the rotational axis of the rotating assembly and thecenter of the mass of the rotating assembly (which has components suchas, but not limited, to the moving coil, the mirror, the moving arm,etc.) is at the center of rotation of the rotating assembly, forexample, as illustrated in FIG. 7 at point 710. Thus in this embodimentwe have the center of mass at the center of rotation (the rotationalaxis) and we have symmetrical torque about the rotational axis. Thisresults in fewer forces that might lead to “wobble” of the rotatingassembly.

FIG. 8 illustrates various embodiments of the present invention.

At 1. A resonant rotational oscillator having a moving coil mounted on amoving member.

At 2. The resonant rotational oscillator of claim 1 wherein said movingcoil is mounted proximate to a mirror mounted on said moving member.

At 3. The resonant rotational oscillator of claim 1 wherein said movingcoil is a plurality of moving coils.

At 4. The resonant rotational oscillator of claim 1 wherein said movingcoil is powered by conductive means mounted on said moving member.

At 5. The resonant rotational oscillator of claim 4 wherein saidconductive means are printed circuit board traces on said moving member.

At 6. The resonant rotational oscillator of claim 1 wherein saidconductive means are electrically connected to two or more flexures.

At 7. The resonant rotational oscillator of claim 2 wherein said movingcoil is a shape as viewed normal to said moving member said shapeselected from the group consisting of rounded rectangular, rectangular,circular, and elliptical.

At 8. The resonant rotational oscillator of claim 1 wherein said movingcoil has an opening through which a magnetic piece protrudes.

At 9. The resonant rotational oscillator of claim 8 wherein saidmagnetic piece is a permanent magnet.

At 10. The resonant rotational oscillator of claim 1 wherein saidmagnetic piece is magnetically coupled to a back iron assembly, saidback iron assembly having one or more pole pieces to concentrate amagnetic flux through said moving coil.

At 11. A resonant rotational oscillator comprising:

a plurality of bending flexures;

a moving member fixedly attached to two or more of said plurality ofbending flexures;

and wherein said resonant rotational oscillator has a performance metric(PM) of greater than 12500 HzDegrees where PM is defined by a equation:PM=frequency*anglewhere:frequency=hertz (Hz) of operation of said resonant rotationaloscillator; andangle=degrees of angle deflection (maximum) of said moving member whenoperating at said frequency.

At 12. The resonant rotational oscillator of claim 11 further comprisinga moving coil mounted on said moving member.

At 13. The resonant rotational oscillator of claim 12 wherein saidplurality of bending flexures is four bending flexures.

At 14. The resonant rotational oscillator of claim 12 wherein two ofsaid plurality of bending flexures are proximate to each other and crossat substantially right angles when viewed along a longitudinal axis ofsaid moving member.

At 15. The resonant rotational oscillator of claim 14 further comprisinga magnetic means for producing a magnetic field across said moving coil.

At 16. The resonant rotational oscillator of claim 15 wherein saidmagnetic means further comprises a permanent magnet.

At 17. An apparatus comprising:

a rigid base having one or more mounting points;

a plurality of flexing members each of said plurality of flexing membershaving a first end and a second end wherein each of said plurality offlexing member's first end is attached to one or more of said one ormore mounting points on said rigid base;

a moving member having a plurality of mounting points;

a plurality of spacing members each of said spacing members having afirst end and a second end wherein each of said plurality of spacingmember's first end is attached to one or more of said plurality ofmounting points on said moving member; and wherein each of saidplurality of spacing member's second end is attached to one or more ofsaid plurality of flexing members second end.

At 18. The apparatus of claim 17 wherein said plurality of flexingmembers is four flexing members.

At 19. The apparatus of claim 17 wherein said spacing members are anintegral part of said plurality of flexing members.

At 20. The apparatus of claim 17 wherein said rigid base, and saidplurality of flexing members, and said moving member, and said pluralityof spacing members are all formed as one integral unit.

At 21. A resonant rotational oscillator having a moving entity on arotating assembly wherein said rotating assembly's center of mass is atsaid rotating assembly's center of rotation.

At 22. The resonant rotational oscillator of claim 21 wherein saidmoving entity applies a symmetrical torque about said rotatingassembly's rotational axis.

At 23. The resonant rotational oscillator of claim 21 wherein saidmoving entity is a moving coil.

At 24. The resonant rotational oscillator of claim 21 wherein saidmoving entity is a moving magnet.

At 25. The resonant rotational oscillator of claim 22 wherein saidmoving entity is a moving coil.

At 26. The resonant rotational oscillator of claim 22 wherein saidmoving entity is a moving magnet.

At 27. A method for producing a resonant rotational oscillator havingits rotating assembly center of mass at its center of rotation, themethod comprising:

attaching a first end of each of a plurality of flexures to a rigidbase;

attaching a second end of each of said plurality of flexures each to afirst end of a plurality of spacers;

attaching a second end of each of said plurality of spacers each to amoving arm wherein said moving arm is a part of said rotating assembly;and

mounting on said moving arm a moving entity.

At 28. The method of claim 27 wherein said moving entity is selectedfrom the group consisting of a moving coil, and a moving magnet.

At 29. The method of claim 28 further comprising wherein said movingentity produces symmetrical torque about said rotating assembly'srotational axis.

In one embodiment of the design for the present invention, the arm couldbe made of an alternative material, for example aluminum, a plastic,graphite, ceramic, glass, or a composite.

In one embodiment of the design for the present invention, the arm couldbe shaped in other variations. The arm could be shaped differently toaccommodate different orientations of the motor, mirror, flexures, andmotion sensor. The section of the arm that supports the mirror could beshaped differently to optimize support in various applications, forexample wider or with a cross bar.

In one embodiment of the design for the present invention, the arm couldbe contoured to allow the mirror to be embedded in the arm to furtherminimize the moment of inertia. Such a contour might appear in profileas a “U” shaped indentation in the arm. Alternatively, the mirror couldbe made integral to the arm by applying the appropriate coating directlyto arm.

In one embodiment of the invention the center of mass (of the movingassembly, also called the rotating assembly) is at the center ofrotation (of the moving assembly). In one embodiment of the inventionsymmetrical torque about the rotational axis is applied (e.g. by amotor). In one embodiment of the invention for the moving assembly thecenter of mass is at the center of rotation and there is symmetricaltorque about the rotational axis.

In one embodiment of the design for the present invention, for differentapplications, the mirror could be replaced with a grating, prism, lens,filter or other optical device. Non-optical applications for the presentinvention are also conceivable, including applications as diverse astissue stimulation and mechanical separation devices.

Thus, the above examples and embodiments should not be deemed to be theonly embodiments, and are presented to illustrate the flexibility andadvantages of the present invention as disclosed. For example there areother means of attaching the flexures to the arm and to the base, forexample welding, soldering, gluing or riveting. Rather than a flat armand attaching flexure spacers, the arm may be formed of a singlematerial to mechanically incorporate both and thereby decrease the totalmass and possibly reduce manufacturing processes. Other types of motorsand motion sensors could be used. The present invention, as oneembodiment, was actually designed with the drive electronicsincorporated into the base.

In the embodiments discussed and disclosed above, a moving coil was usedto illustrate various embodiments, however, the invention is not solimited. In other embodiments a moving magnet may be used rather than amoving coil. Thus a moving magnet motor may be used rather than a movingcoil motor. One of skill in the art will understand that where a movingmagnet is used a coil may be used to cause the moving magnet to rotate.

Thus a method and apparatus for resonant rotational oscillator have beendescribed.

For purposes of discussing and understanding the invention, it is to beunderstood that various terms are used by those knowledgeable in the artto describe techniques and approaches. Furthermore, in the description,for purposes of explanation, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be evident, however, to one of ordinary skill in the art that thepresent invention may be practiced without these specific details. Insome instances, well-known structures and devices are shown in blockdiagram form, rather than in detail, in order to avoid obscuring thepresent invention. These embodiments are described in sufficient detailto enable those of ordinary skill in the art to practice the invention,and it is to be understood that other embodiments may be utilized andthat logical, mechanical, electrical, and other changes may be madewithout departing from the scope of the present invention.

Some portions of the description may be presented in terms of algorithmsand symbolic representations of operations on, for example, data bitswithin a computer memory. These algorithmic descriptions andrepresentations are used by those of ordinary skill in the dataprocessing arts to most effectively convey the substance of their workto others of ordinary skill in the art. An algorithm is here, andgenerally, conceived to be a self-consistent sequence of acts leading toa desired result. The acts are those requiring physical manipulations ofphysical quantities. Usually, though not necessarily, these quantitiestake the form of electrical or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated. It hasproven convenient at times, principally for reasons of common usage, torefer to these signals as bits, values, elements, symbols, characters,terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate non-transitory physicalquantities and are merely convenient labels applied to these quantities.Unless specifically stated otherwise as apparent from the discussion, itis appreciated that throughout the description, discussions utilizingterms such as “processing” or “computing” or “calculating” or“determining” or “displaying” or the like, can refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission, or display devices.

It is to be understood that various terms and techniques are used bythose knowledgeable in the art to describe communications, protocols,applications, implementations, mechanisms, etc. One such technique isthe description of an implementation of a technique in terms of analgorithm or mathematical expression. That is, while the technique maybe, for example, implemented as executing code on a computer, theexpression of that technique may be more aptly and succinctly conveyedand communicated as a formula, algorithm, or mathematical expression.Thus, one of ordinary skill in the art would recognize a block denotingA+B=C as an additive function whose implementation in hardware and/orsoftware would take two inputs (A and B) and produce a summation output(C). Thus, the use of formula, algorithm, or mathematical expression asdescriptions is to be understood as having a physical embodiment in atleast hardware and/or software (such as a specialized computer system inwhich the techniques of the present invention may be practiced as wellas implemented as an embodiment).

As used in this description, “one embodiment” or “an embodiment” orsimilar phrases means that the feature(s) being described are includedin at least one embodiment of the invention. References to “oneembodiment” in this description do not necessarily refer to the sameembodiment; however, neither are such embodiments mutually exclusive.Nor does “one embodiment” imply that there is but a single embodiment ofthe invention. For example, a feature, structure, act, etc. described in“one embodiment” may also be included in other embodiments. Thus, theinvention may include a variety of combinations and/or integrations ofthe embodiments described herein.

As used in this description, “substantially” or “substantially equal” orsimilar phrases are used to indicate that the items are very close orsimilar. Since two physical entities can never be exactly equal, aphrase such as “substantially equal” is used to indicate that they arefor all practical purposes equal.

It is to be understood that in any one or more embodiments of theinvention where alternative approaches or techniques are discussed thatany and all such combinations as may be possible are hereby disclosed.For example, if there are five techniques discussed that are allpossible, then denoting each technique as follows: A, B, C, D, E, eachtechnique may be either present or not present with every othertechnique, thus yielding 2^5 or 32 combinations, in binary order rangingfrom not A and not B and not C and not D and not E to A and B and C andD and E. Applicant(s) hereby claims all such possible combinations.Applicant(s) hereby submit that the foregoing combinations comply withapplicable EP (European Patent) standards. No preference is given anycombination.

Thus a method and apparatus for resonant rotational oscillator have beendescribed.

What is claimed is:
 1. A resonant rotational oscillator having a moving coil mounted on a moving member, said moving member having four or more terminating ends, said terminating ends attached to four or more flat flexures, pairs of said flat flexures arranged to cross substantially at right angles when viewed along a longitudinal axis of said moving member, wherein said resonant rotational oscillator has a performance metric (PM) of greater than 12500 HzDegrees where PM is defined by an equation: PM=frequency*angle where: frequency=hertz (Hz) of operation of said resonant rotational oscillator; and angle=degrees of angle deflection (maximum) of said moving member when operating at said frequency.
 2. The resonant rotational oscillator of claim 1 further comprising a moving coil mounted on said moving member.
 3. The resonant rotational oscillator of claim 2 wherein said four or more flat flexures is four flat flexures.
 4. The resonant rotational oscillator of claim 3 further comprising a magnetic means for producing a magnetic field across said moving coil.
 5. The resonant rotational oscillator of claim 4 wherein said magnetic means further comprises a permanent magnet.
 6. The resonant rotational oscillator of claim 2 wherein two of said plurality of bending flexures are proximate to each other and cross at substantially right angles when viewed along a longitudinal axis of said moving member. 